Methods of Forming Connector Pad Structures, Interconnect Structures, and Structures Thereof

ABSTRACT

Methods of forming connector pad structures, interconnect structures, and structures thereof are disclosed. In some embodiments, a method of forming a connector pad structure includes forming an underball metallization (UBM) pad, and increasing a surface roughness of the UBM pad by exposing the UBM pad to a plasma treatment. A polymer material is formed over a first portion of the UBM pad, leaving a second portion of the UBM pad exposed.

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 14/815,584, filed on Jul. 31, 2015, and entitled,“Methods of Forming Connector Pad Structures, Interconnect Structures,and Structures Thereof,” which application is incorporated herein byreference.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment. Semiconductor devices are typically fabricated bysequentially depositing insulating or dielectric layers, conductivelayers, and semiconductive layers of material over a semiconductorsubstrate, and patterning the various material layers using lithographyto form circuit components and elements thereon. Dozens or hundreds ofintegrated circuits are typically manufactured on a single semiconductorwafer. The individual dies are singulated by sawing the integratedcircuits along scribe lines. The individual dies are then packagedseparately, in multi-chip modules, or in other types of packaging.

The semiconductor industry continues to improve the integration densityof various electronic components (e.g., transistors, diodes, resistors,capacitors, etc.) by continual reductions in minimum feature size, whichallow more components to be integrated into a given area. These smallerelectronic components also require smaller packages that utilize lessarea than packages of the past, in some applications.

One type of smaller packages for semiconductor devices that has beendeveloped are wafer level packages (WLPs), in which integrated circuitsare packaged in packages that typically include a redistribution layer(RDL) or post-passivation interconnect (PPI) that is used to fan-outwiring for contact pads of the package so that electrical contacts maybe made on a larger pitch than contact pads of the integrated circuit.WLPs are often used to package integrated circuits (ICs) that demandhigh speed, high density, and greater pin count, as examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 7 are cross-sectional views of a portion of a packagedsemiconductor device at various stages that illustrate a method offorming a connector pad structure and an interconnect structure inaccordance with some embodiments of the present disclosure.

FIG. 8 is a graph showing stages of a reflow process for a material of aconnector in accordance with some embodiments.

FIG. 9 shows a top view of a connector shown in FIG. 7 that includes aflux residue disposed around edges thereof in accordance with someembodiments.

FIG. 10 shows the connector shown in FIG. 9 after a removal of the fluxresidue in accordance with some embodiments.

FIG. 11 shows a cross-sectional view of the connector shown in FIG. 10in accordance with some embodiments.

FIG. 12 illustrates a cross-sectional view of a portion of a packagedsemiconductor device that includes a plurality of the connectors shownin FIG. 11 in accordance with some embodiments.

FIG. 13 is a cross-sectional view illustrating a packaged semiconductordevice in accordance with some embodiments.

FIG. 14 shows a cross-sectional view of a package-on-package (POP)device in accordance with some embodiments.

FIG. 15 is a flow chart that illustrates a method of forming a connectorpad structure in accordance with some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Methods of forming connector pad structures, methods of forminginterconnect structures, interconnect structures, and packagedsemiconductor devices that include the connector pad structures andinterconnect structures are disclosed in the present disclosure. Theconnector pad structures and interconnect structures include anintermetallic compound (IMC) that is formed between connectors andunderball metallization (UBM) pads, wherein the IMC is not formedbetween edges of the UBM pads and a polymer material proximate edges ofthe UBM pads, which improves reliability. Some embodiments are disclosedthat utilize connector pad structures and interconnect structures thatmay be used for the purpose of attaching one substrate to anothersubstrate, wherein the substrates may be a die, wafer, printed circuitboard (PCB), packaging substrate, or the like, thereby allowing fordie-to-die, wafer-to-die, wafer-to-wafer, die or wafer to printedcircuit board, packaging substrate types of packaging, or the like.Throughout the various views and illustrative embodiments, likereference numerals are used to designate like elements.

FIGS. 1 through 7 are cross-sectional views of a portion of a packagedsemiconductor device at various stages that illustrate a method offorming a connector pad structure 101 and interconnect structure 100 inaccordance with some embodiments of the present disclosure. Referringfirst to FIG. 1, in some embodiments, an interconnect structure 100 thatincludes a redistribution layer (RDL) 106 is formed over a carrier 102.The carrier 102 comprises a wafer, tape, or other type of support,substrate, or device that may be used for a packaging process as aplatform for packaging one or more integrated circuit dies 152. Thecarrier 102 is later removed after the packaging process in someembodiments, for example. The carrier 102 includes an integrated circuitdie 152 (not shown in FIG. 1; see FIG. 12) that is encapsulated disposedthereon in some embodiments, to be described further herein.

The RDL 106 comprises a plurality of conductive lines 108 and conductivevias 110 formed in a plurality of insulating material layers 104 a. Oneconductive line 108 and one conductive via 110 are shown in FIGS. 1through 7 and 11; however, a plurality of the conductive lines 108 andconductive vias 110 are formed over the carrier 102. The RDL 106comprises a post-passivation interconnect (PPI) structure in someembodiments, wherein the conductive lines 108 comprise PPI lines, forexample. The RDL 106 may also comprise other types of wiring. The RDL106 provides electrical connections in a horizontal direction for apackaged semiconductor device (see packaged semiconductor device 150shown in FIG. 12) in some embodiments, for example.

Referring again to FIG. 1, the plurality of insulating material layers104 a may comprise a dielectric material such as SiO₂, SiN,plasma-enhanced oxide (PEOX), plasma-enhanced SiN (PE-SiN),plasma-enhanced undoped silicate glass (PE-USG), polybenzoxazole (PBO),polyimide (PI), epoxy, benzocyclobutene (BCB), molding compound, and thelike, or a combination of multiple layers thereof. The conductive lines108 and conductive vias 110 may comprise a conductive material such ascopper, a copper alloy, or other metals or conductive materials in someembodiments that is formed using a plating process or other depositionprocess within the insulating material layers 104 a. The plurality ofinsulating material layers 104 a is patterned using one or morelithography processes, which can include forming a layer of photoresist(not shown) over the plurality of insulating material layers 104 a, andexposing the photoresist to light or energy reflected from or through alithography mask (also not shown) having a desired pattern thereon. Thephotoresist is then developed, and exposed (or unexposed, depending onwhether the photoresist is a positive or negative photoresist) portionsof the photoresist are removed to form a patterned layer of photoresist.The patterned layer of photoresist is then used as an etch mask duringan etch process for the plurality of insulating material layers 104 a.The layer of photoresist is then removed using an ashing and/or etchprocess.

The conductive lines 108 and conductive vias 110 may comprise a thinlayer, e.g., comprising a thickness of about 2 μm to about 3 μm or less,of titanium or other seed material that is formed using a sputteringprocess, and a layer of copper, a copper alloy, or other metal that iselectro-plated over the layer of titanium, in some embodiments. In otherembodiments, the conductive lines 108 and conductive vias 110 maycomprise a multi-layered structure, such as a copper layer coated withelectro-less nickel or electro-less palladium immersion gold (ENEPIG),which includes a nickel layer, a palladium layer on the nickel layer,and a gold layer on the palladium layer. The gold layer may be formedusing immersion plating. The conductive lines 108 and conductive vias110 may also comprise other materials, dimensions, and formationmethods. The plurality of insulating material layers 104 a is thenformed around the conductive lines 108 and conductive vias 110.

In some embodiments, the conductive lines 108 and conductive vias 110may be deposited and patterned using a lithography process, similar tothe lithography process described for the plurality of insulatingmaterial layers 104 a, using an etch chemistry suited for the materialof the conductive lines 108 and conductive vias 110. For example, aconductive material may be formed as a blanket coating and then etchedusing a lithography process to pattern the conductive lines 108 andconductive vias 110.

A plurality of insulating material layers 104 b is formed over theconductive lines 108 and conductive vias 110 and the plurality ofinsulating material layers 104 a. The plurality of insulating materiallayers 104 b may comprise similar materials as described for theplurality of insulating material layers 104 a, for example. Theplurality of insulating material layers 104 a and 104 b are labeledcollectively as an insulating material 104 in some of the drawings ofthe present disclosure. The plurality of insulating material layers 104b is patterned using lithography to expose a portion of the conductivelines 108.

A plurality of UBM pads 112 is formed over the RDL 106. One UBM pad 112is shown in FIGS. 1 through 7 and 11; however, a plurality of the UBMpads 112 is formed over the carrier 102 over the RDL 106. The pluralityof UBM pads 112 is electrically and mechanically coupled to theconductive lines 108 of the RDL 106. Each of the plurality of UBM pads112 may be coupled to one of the conductive lines 108, for example, asshown in FIG. 1. Each of the plurality of UBM pads 112 may also becoupled to one of the conductive vias 110 (not shown), or each of theplurality of UBM pads 112 may also be coupled to one of the conductivelines 108 and/or conductive vias 110, for example.

The plurality of UBM pads 112 comprises copper, a copper alloy, or othermetals in some embodiments, for example, that is formed using a platingprocess, as described for the conductive lines 108 and conductive vias110 of the RDL 106. The plurality of UBM pads 112 may comprise athickness of about 5 μm to about 7 μm, for example. The plurality of UBMpads 112 may also comprise other materials, dimensions, and formationmethods. The plurality of UBM pads 112 is formed within the plurality ofinsulating material layers 104 b over the RDL 106, for example. Each ofthe plurality of UBM pads 112 is adapted to have a connector 132 (seeFIG. 5) coupled thereto. In some embodiments, an upper portion of theplurality of insulating material layers 104 b comprises a recess 113proximate edges 136 of the plurality of UBM pads 112. The recess 113proximate the edges 136 of the plurality of UBM pads 112 will later befilled with a polymer material 120 (see FIG. 3), for example. In otherembodiments, a recess 113 is not included in the insulating materiallayers 104 b proximate the edges 136 of the plurality of UBM pads 112,not shown.

The RDL 106 and the plurality of UBM pads 112 are formed using a waferlevel package (WLP) process in some embodiments, for example.

Referring again to FIG. 1, the plurality of UBM pads 112 comprises afirst surface roughness 116. The first surface roughness 116 of theplurality of UBM pads 112 has an average surface roughness or R_(a) ofless than about 0.18 μm in some embodiments, after the formation of theplurality of UBM pads 112, for example. The first surface roughness 116may also comprise other values. The first surface roughness 116 of theplurality of UBM pads 112 has an initial surface roughness after theformation of the plurality of UBM pads 112, for example.

The first surface roughness 116 of the plurality of UBM pads 112 isincreased to a higher level of roughness or a more increased surfaceroughness in accordance with some embodiments. The first surfaceroughness 116 of the top surface of the plurality of UBM pads 112 isaltered to a second surface roughness 118 (see FIG. 2), the secondsurface roughness 118 being greater than the first surface roughness116, in some embodiments, for example.

To alter the first surface roughness 116, the plurality of UBM pads 112is exposed to a plasma treatment 114 in some embodiments, as shown inFIG. 1. The plasma treatment 114 comprises a duration time of about 100seconds or less in the presence of N₂ and at a chamber temperature ofabout 50 degrees C. to about 100 degrees C. in some embodiments, forexample. The plasma treatment 114 may also comprise other processingparameters. The first surface roughness 116 of the plurality of UBM pads112 is increased to the second surface roughness 118 by the plasmatreatment 114 in some embodiments, as illustrated in FIG. 2. The plasmatreatment 114 roughens the UBM pad 112 surface, for example. The secondsurface roughness 118 has an average surface roughness or R_(a) of about0.18 μm to about 0.25 μm in some embodiments, for example. The secondsurface roughness 118 is a value sufficient to improve adhesion of asubsequently deposited polymer material 120 (see FIG. 3), for example.The second surface roughness 118 may also be other values. The firstsurface roughness 116 of the plurality of UBM pads 112 may also bealtered using other methods, such as by altering a plating processcondition, as an example.

The polymer material 120 is then formed over the insulating material 104and a first portion 122 of the plurality of UBM pads 112, as shown inFIG. 3. The polymer material 120 may be formed using a blanketdeposition process, for example. The polymer material 120 issubstantially conformal in some embodiments and substantially covers anentire surface of the interconnect structure 100, as shown in phantom(e.g., in dashed lines) in FIG. 3 at 120′. The polymer material 120comprises an insulating material such as PBO, PI, epoxy, BCB, moldingcompound, and/or a combination thereof, as examples. The polymermaterial 120 may comprise a thickness over the plurality of UBM pads 112of about 6 μm to about 8 μm, for example. The polymer material 120 mayalso comprise other materials, dimensions, and formation methods.

The polymer material 120 is patterned using a lithography process,leaving the polymer material 120 in predetermined locations over theinterconnect structure 100. The polymer material 120 is patterned toexpose a second portion 124 of the plurality of UBM pads 112. Thepolymer material 120 is left remaining on a first portion 122 of theplurality of UBM pads 112, and the second portion 124 of the pluralityof UBM pads 112 is left exposed. The polymer material 120 is disposedover the surfaces of the plurality of UBM pads 112 over the firstportion 122 of the plurality of UBM pads 112. The increased roughness(i.e., the second surface roughness 118) of the plurality of UBM pads112 advantageously increases adhesion between the polymer material 120and the first portion 122 of the plurality of UBM pads 112, forming amore robust interface of the polymer material 120 and the first portion122 of the plurality of UBM pads 112 in some embodiments.

In some embodiments, the first portion 122 of the plurality of UBM pads112 comprise edge regions of the plurality of UBM pads 112, and thesecond portion 124 of the plurality of UBM pads 112 comprisesubstantially central regions of the plurality of UBM pads 112, forexample. The first portion 122 and the second portion 124 of theplurality of UBM pads 112 may also comprise other regions of theplurality of UBM pads 112.

In some embodiments, a method of forming a connector pad structure 101shown in FIG. 3 includes forming a UBM pad 112, and exposing the UBM pad112 to the plasma treatment 114 as shown in FIG. 1. The method includesforming the polymer material 120 over the first portion 122 of the UBMpad 112 yet leaving the second portion 124 of the UBM pad 112 exposed.In some embodiments, a method of forming a connector pad structure 101may further comprise forming a flux 128 over the exposed second portion124 of the UBM pads 112, as shown in FIGS. 4 and 5, which will next bedescribed.

In some embodiments, a flux stencil 126 is provided and is disposedproximate the interconnect structure 100, as illustrated in FIG. 4. Theflux stencil 126 (i.e., an opening in the flux stencil 126) is placedproximate each of the plurality of UBM pads 112, for example. Openingsin the flux stencil 126 are disposed proximate the exposed secondportions 124 of the plurality of UBM pads 112. The flux 128 is thenapplied using a method such as printing the flux 128 over the pluralityof UBM pads 112, for example. The flux 128 may be applied using a flat,smooth blade such as a squeegee over the flux stencil 126, for example.The flux 128 may also be applied using other methods or tools. The fluxstencil 126 is then removed.

The flux 128 comprises a low activity flux in some embodiments that isadapted to not damage or react with an interface region of the pluralityof UBM pads 112 and the polymer material 120 disposed over the firstportions 122 of the plurality of UBM pads 112, in some embodiments. Theflux 128 does not damage or react with the interface region because thelow activity flux 128 comprises a material that does not react with thepolymer material 120. The flux 128 comprises a material that is adaptedto improve a connection of a subsequently formed connector 132 (see FIG.5) over the plurality of UBM pads 112, in some embodiments. The flux 128improves the connection of the connector 132 by deoxidizing a nativeoxide layer on the UBM pad 112 surface in some embodiments, for example.The flux 128 comprises a material that is adapted to assist in andfacilitate a removal of oxide from a surface of the plurality of UBMpads 112, if oxide is present, in some embodiments, for example. Theflux 128 may comprise a thickness of about 10 μm or less after the flux128 is formed over the second portions 124 of the plurality of UBM pads112 in some embodiments, for example. The flux 128 may also compriseother properties, types of materials, and dimensions.

Before, during, and/or after the flux 128 is applied, an oxide layer 134may form over a top surface of the second portion 124 of the pluralityof UBM pads 112, as shown in FIG. 5. The oxide layer 134 may form due tooxidation of the exposed top surface of the plurality of UBM pads 112,for example. The oxide layer 134 may comprise a material of theplurality of UBM pads 112 and oxygen, such as CuO₂, for example. Theoxide layer 134 may comprise a native oxide in some embodiments, forexample. The oxide layer 134 may comprise a thickness of a few μm, suchas about 300 Angstroms to about 1 μm or less, for example. The oxidelayer 134 may also comprise other materials and dimensions. The flux 128advantageously assists in the removal of the oxide layer 134 during asubsequent reflow process for a connector 132 in some embodiments. Insome embodiments, an oxide layer 134 is not formed.

After the application of the flux 128, as shown in FIG. 4, a stencil 130is placed proximate the interconnect structure 100 in some embodiments,as shown in FIG. 5. The stencil 130 comprises a solder ball stencil insome embodiments, for example. The stencil 130 may also comprise othertypes of stencils. The stencil 130 is placed proximate the plurality ofUBM pads 112, for example. A material of a connector 132 is then applied(i.e., brushed on or other methods) onto the flux 128 residing over theplurality of UBM pads 112, through openings in the stencil 130, forminga connector 132 over each of the plurality of UBM pads 112. After theformation of the material of the connectors 132, the stencil 130 isremoved, as shown in FIG. 6. In some embodiments, a stencil 130 is notused to attach the material of the connectors 132, as another example.The connectors 132 may be attached using a ball mount process in someembodiments, for example. The material of the connectors 132 may also beapplied using a spin-on process, a solder bath, or solder pasteprinting, as examples. The material of the connector 132 may also beformed using other methods and may comprise other materials.

The material of the connectors 132 comprises a eutectic material such assolder. The use of the word “solder” herein includes both lead-based andlead-free solders, such as Pb—Sn compositions for lead-based solder;lead-free solders including InSb; tin, silver, and copper (“SAC”)compositions; and other eutectic materials that have a common meltingpoint and form conductive solder connections in electrical applications.For lead-free solder, SAC solders of varying compositions may be used,such as SAC 105 (Sn 98.5%, Ag 1.0%, Cu 0.5%), SAC 305, and SAC 405, asexamples. Lead-free conductive materials such as solder balls may beformed from SnCu compounds as well, without the use of silver (Ag).Lead-free solder connectors may also include tin and silver, Sn—Ag,without the use of copper.

The connectors 132 over the plurality of UBM pads 112 are coupled in asubstantially central region of the second portions 124 of the pluralityof UBM pads 112 in some embodiments after the formation of the materialof the connectors 132, as illustrated in FIG. 5. The material of theconnectors 132 may not be coupled to edge regions of the second portions124 of the plurality of UBM pads 112 in some embodiments after theformation of the material of the connectors 132, which is alsoillustrated in FIG. 5.

The material of the connectors 132 is then heated to a predeterminedtemperature, e.g., to a melting point of the eutectic material of thematerial of the connectors 132, such as about 150 degrees C. to about270 degrees C., to reflow the material of the connectors 132. Theconnector 132 material may be heated by heating the interconnectstructure 100, which causes the flux 128 to interact with the oxidelayer 134 (if present) and a top surface of the plurality of UBM pads112, resulting in the removal of the oxide layer 134, which isillustrated in FIG. 6. The interconnect structure 100 is continued to beheated until a melting point of a eutectic material of the material ofthe connector 132 is reached, causing a reflow of the material of theconnectors 132 and an electrical and mechanical connection of aconnector 132 to each of the plurality of UBM pads 112, as illustratedin FIG. 7.

In some embodiments, the connectors 132 may comprise solder bumps orsolder balls, as examples. The connectors 132 comprise conductive ballshaving a shape of a partial sphere in some embodiments. The connectors132 may have a height of about 170 μm or less in some embodiments, forexample. The connectors 132 may also comprise other dimensions andshapes. The connectors 132 may also comprise non-spherical conductiveconnectors, for example. The connectors 132 may be included in an arrayof the connectors 132 as a grid, referred to as a “ball grid array” or“BGA”. The connectors 132 may also be arranged in other shapes.

The reflow of the material of the connectors 132 improves adhesion ofthe connectors 132 to the UBM pads 112 and more completely attaches theconnectors 132 to the plurality of UBM pads 112. The reflow processresults in the material of the connectors 132 being coupled over centralregions and also edge regions of the second portions 124 of the UBM pads112 in some embodiments, as illustrated in FIG. 7. In some embodiments,a portion of the flux 128 comprising a flux residue 128′ is leftresiding around the edges of the connectors 132 after the reflowprocess, which is also illustrated in FIG. 7. In accordance with someembodiments, the flux residue 128′ is then removed using a cleaningprocess, which will be described further herein.

FIG. 7 also illustrates an IMC 140 that is formed between the connectors132 and the plurality of UBM pads 112 during the reflow of the eutecticmaterial of the connectors 132. The IMC 140 is disposed over thesurfaces of the plurality of UBM pads 112 over the second portions 124of the plurality of UBM pads 112. The IMC 140 is advantageously notformed between the first portions 122 of the plurality of UBM pads 112and the polymer material 120 in some embodiments, due to the increasedsecond surface roughness 118 of the top surface of the plurality of UBMpads 112, in accordance with some embodiments of the present disclosure.Using a flux 128 comprising a low activity flux further assists inreducing or preventing a portion of the IMC 140 from forming over thefirst portions 122 of the plurality of UBM pads 112, between the polymermaterial 120 and the first portions 122 of the plurality of UBM pads112, in some embodiments, for example. Reflowing the material of theconnectors 132 does not comprise forming the IMC 140 between the firstportions 122 of the plurality of UBM pads 112 and the polymer material120 in some embodiments, for example.

The IMC 140 may comprise CuSn, for example, in some embodiments whereinthe connectors 132 comprise Sn. The IMC 140 may comprise CuSn, Ag₃Sn,Cu₃Sn, Cu₆Sn₅ in some embodiments, as examples. The IMC 140 may comprisea thickness of about 0.5 μm to about 2 μm in some embodiments, or about0.75 μm in some embodiments, as examples. The IMC 140 comprises amaterial and dimension sufficient to improve electrical connection ofthe connectors 132 to the plurality of UBM pads 112, for example.

FIG. 8 is a graph that shows some stages of a reflow process for amaterial of the connector 132 in accordance with some embodiments. Timein seconds (sec.) is illustrated on an x-axis of the graph, andtemperature in degrees C. is illustrated on a y-axis of the graph. Thetime period between zero and about 60 seconds comprises an initialregion 141 wherein the material of the connector 132 is initiallyheated. The time period between about 60 seconds and about 130 secondscomprises a soaking region 142. The duration of the soaking region 142comprises about 70 seconds in some embodiments, as an example. As thetemperature is increased over time, the connector 132 reaches a dwellregion 144 at about 240 seconds plus or minus about 20 seconds, at whichpoint a eutectic material of the connector 132 reflows. The duration ofthe dwell region 144 comprises about 50 seconds in some embodiments, asan example. The dwell region 144 comprises a peak temperature 146 atwhich the material of the connector 132 is melted, for example. The peaktemperature 146 comprises about 220 degrees C. in the example shown. Amelting temperature comprising the peak temperature 146 may compriseabout 200 degrees C. to about 250 degrees C. in some embodiments, asanother example, depending on the material used for the plurality ofconnectors 132, for example. The peak temperature 146 and the durationsof the soaking region 142 and the dwell region 144 may also compriseother values. The temperature is then lowered, and the eutectic materialof the connector 132 resolidifies, mechanically and electricallycoupling the connector 132 to substantially the entire exposed topsurfaces of the plurality of UBM pads 112, e.g., over the secondportions 124 of the plurality of UBM pads 112, over the IMC 140, in someembodiments.

The use of a low activity flux material for the flux 128 may preventinterface damage between the polymer material 120 and the first portions122 of the plurality of UBM pads 112 during the soaking region 142 ofthe reflow process. Thus, migration of the material of the connectors132 into the interface of the polymer material 120 and the firstportions 122 of the plurality of UBM pads 112 during the dwell region144 of the reflow process is prevented, in some embodiments.

FIG. 9 shows a top view of a connector 132 attached to one of theplurality of UBM pads 112 shown in FIG. 7 that includes a flux residue128′ disposed around edges of the connector 132 in accordance with someembodiments. Edges 136 of the UBM pad 112 extend past the connector 132and the flux residue 128′. The first portion 122 of the UBM pad 112extends past the second portion 124 towards the edges 136 of the UBM pad112. In accordance with some embodiments of the present disclosure, theinterconnect structure 100 is cleaned using a cleaning process to removethe flux residue 128′. The flux residue 128′ is cleaned using a fluxcleaning machine in some embodiments, for example. The flux residue 128′may also be removed using other devices and methods.

FIG. 10 shows a top view of the connector 132 shown in FIG. 9 after theremoval of the flux residue 128′ using the cleaning process inaccordance with some embodiments. FIG. 11 is a cross-sectional view ofthe connector 132 shown in FIG. 10 in accordance with some embodiments.The oxide layer 134 has been removed by the flux 128 during the reflowprocess for the connector 132. The increased second surface roughness118 improves the adhesion between the polymer material 120 and the firstportion 122 of the UBM pad 112 so that the IMC 140 is advantageously notformed between the polymer material 120 and the first portion 122 of theUBM pad 112, which improves reliability.

FIG. 12 illustrates a cross-sectional view of a portion of a packagedsemiconductor device 150 that includes a plurality of the connectors 132shown in FIG. 11 in accordance with some embodiments. The interconnectstructure 100 includes a plurality of the connectors 132 coupled to aplurality of UBM pads 112. The IMC 140 is formed between the secondportions 124 of the plurality of UBM pads 112 and the plurality ofconnectors 132. The IMC 140 is advantageously not formed between thepolymer material 120 and the first portions 122 of the plurality of UBMpads 112.

FIG. 12 also illustrates some additional elements of the packagedsemiconductor device 150 in accordance with some embodiments of thepresent disclosure. The packaged semiconductor device 150 includes aninterconnect structure 100 coupled to an integrated circuit die 152, anda molding material 154 disposed around the integrated circuit die 152and beneath the interconnect structure 100. The packaged semiconductordevice 150 comprises fan-out structures in some embodiments. Forexample, conductive wiring of the interconnect structure 100 (e.g., suchas the conductive lines 108 and conductive vias 110 of the RDL 106) maybe spaced apart farther than conductive wiring of the integrated circuitdie 152 is spaced. Likewise, the footprint of UBM pads 112 of theinterconnect structure 100 may be larger than the footprint of contactspads 153 of the integrated circuit die 152. The packaged semiconductordevice 150 comprises an integrated fan-out (InFO) device or a WLP devicein some embodiments. The packaged semiconductor device 150 may alsocomprise other types of packages.

To package the integrated circuit die 152, in some embodiments, afterthe carrier 102 shown in FIG. 1 is provided, before the interconnectstructure 100 is formed over the carrier 102, an integrated circuit die152 is provided and is coupled to the carrier 102. The integratedcircuit die 152 may comprise a substrate having electrical circuitryformed within or thereon. The substrate may comprise, for example, dopedor undoped bulk silicon or an active layer of asemiconductor-on-insulator (SOI) substrate. The electrical circuitry ofthe substrate of the integrated circuit die 152 may be any type ofcircuitry suitable for a particular application. The integrated circuitdie 152 may comprise a logic, memory, processor, or other type ofdevice. As other examples, electrical circuitry formed within or on thesubstrate of the integrated circuit die 152 may include various N-typemetal-oxide semiconductor (NMOS) and/or P-type metal-oxide semiconductor(PMOS) devices, such as transistors, capacitors, resistors, diodes,photo-diodes, fuses, and the like, that are interconnected to performone or more functions. The functions may include memory structures,logic structures, processing structures, sensors, amplifiers, powerdistribution, input/output circuitry, and/or the like. One of ordinaryskill in the art will appreciate that the above examples are providedfor illustrative purposes to further explain applications of someillustrative embodiments and are not meant to limit the disclosure inany manner. Other circuitry may be used as appropriate for a givenapplication. The integrated circuit die 152 typically has beenfabricated by forming a plurality of the integrated circuit dies 152 ona semiconductor wafer, and singulating the individual integrated circuitdies 152 along scribe lines.

The packaging process for the integrated circuit die 152 in someembodiments comprises providing the carrier 102, and attaching one ormore integrated circuit dies 152 to the carrier 102. The carrier 102 islater removed after packaging a plurality of the integrated circuit dies152 in some embodiments, for example.

In some embodiments, through-vias (not shown in FIG. 12; seethrough-vias 156 shown in FIG. 13) are also formed over the carrier 102.The through-vias 156 may be plated on a seed layer (not shown) formed onthe carrier 102, for example. In some embodiments, through-vias 156 arenot included. A plurality of the through-vias 156 may be formed in someembodiments over the carrier 102 by plating, lithography and subtractiveetch processes, or other methods, before or after a plurality of theintegrated circuit dies 152 is coupled to the carrier 102. The pluralityof through-vias 156 may be formed using an electro-plating process, bydepositing a seed layer over the carrier 102, and forming a patternedmask with a desired pattern for the through-vias 156 over the seedlayer. The through-vias 156 are plated onto the carrier 102 through thepatterned mask, and the patterned mask is then removed. The exposedportions of the seed layer are also removed. The through-vias 156 maycomprise copper, a copper alloy, or other metals or conductivematerials. Dozens or hundreds of through-vias 156 may be included in apackage for each of the integrated circuit dies 152 or groups ofintegrated circuit dies 152 that are packaged together, for example. Theplurality of through-vias 156 provides electric connections in avertical direction for the packaged semiconductor devices 150 in someembodiments. Each of the plurality of through-vias 156 may be positionedso that they will be coupled to a conductive portion of the interconnectstructure 100, such as conductive lines 108 and/or conductive vias 110of the RDL 106 that is later formed, for example.

A plurality of the integrated circuit dies 152 is coupled to the carrier102 between some of the plurality of through-vias 156 in someembodiments. One integrated circuit die 152 is shown in the drawings; insome embodiments, a plurality of the integrated circuit dies 152 iscoupled to the carrier 102 and is packaged simultaneously. The pluralityof integrated circuit dies 152 may be coupled to the carrier 102 using adie attach film (DAF) (not shown) disposed on a bottom surface of theintegrated circuit dies 152 in some embodiments. The plurality ofintegrated circuit dies 152 may be placed on the carrier 102 using apick-and-place machine or manually, for example. The integrated circuitdies 152 or two or more integrated circuit dies 152 are later singulatedalong scribe lines (i.e., of the package or interconnect structure 100)to form a plurality of packaged semiconductor devices 150. Theintegrated circuit die 152 includes contact pads 153 formed on a topsurface thereof that are used to electrically connect to portions of theRDL 106, such as conductive vias 110, as illustrated in FIG. 12, in someembodiments.

The molding material 154 is then formed over the carrier 102, over theintegrated circuit die 152 and the through-vias 156, in embodimentswherein the through-vias 156 are included. The molding material 154 maycomprise a molding compound comprised of an insulating material, such asan epoxy, a filler material, a stress release agent (SRA), an adhesionpromoter, other materials, or combinations thereof, as examples. Themolding material 154 may comprise a liquid or gel when applied so thatit flows between a plurality of the integrated circuit dies 152 beingsimultaneously packaged and around the through-vias 156, in someembodiments. The molding material 154 is then cured or allowed to dry sothat it forms a solid. A molding compound clamp may be applied during acuring process and a plasma treatment process of the molding material154 in some embodiments. In some embodiments, as deposited, the moldingmaterial 154 extends over top surfaces of the plurality of integratedcircuit dies 152 and the through-vias 156, and after the moldingmaterial 154 is applied, a top portion of the molding material 154 isremoved using a planarization process, such as a chemical mechanicalpolish (CMP) process, a grinding process, an etch process, orcombinations thereof, as examples. Other methods may also be used toplanarize the molding material 154. A top portion of the integratedcircuit dies 152 and/or through-vias 156 may also be removed during theplanarization process for the molding material 154. In some embodiments,an amount of the molding material 154 applied may be controlled so thattop surfaces of the integrated circuit dies 152 and through-vias 156 areexposed. Other methods may also be used to form the molding material154.

The interconnect structure 100 may then be formed over the planarizedmolding material 154, the integrated circuit dies 152, and thethrough-vias 156. The interconnect structure 100 comprises the RDL 106and/or a PPI in some embodiments. The interconnect structure 100 mayinclude one, two, or several conductive line layers and via layers. Someof the conductive lines 108 and/or conductive vias 110 of theinterconnect structure 100 are coupled to contact pads 153 of theintegrated circuit die 152.

The carrier 102 wafer is then removed in some embodiments. In someembodiments, a plurality of the packaged semiconductor devices 150 isthen singulated to form the packaged semiconductor device 150 shown inFIG. 12. The packaged semiconductor devices 150 may be singulated usinga saw or laser (not shown), which may include a blade comprising diamondor other materials in some embodiments, for example. One or morecarriers 102 may be used to package a semiconductor device.

FIG. 13 is a cross-sectional view of a packaged semiconductor device 150in accordance with some embodiments. The packaged semiconductor device150 shown in FIG. 13 has been inverted from the view of the packagedsemiconductor device 150 shown in FIG. 12, for example. The interconnectstructure 100 comprises a first interconnect structure 100 of thepackaged semiconductor device 150, and a second interconnect structure100′ has been formed on an opposite side of the packaged semiconductordevice 150 from the first interconnect structure 100. A plurality ofconnectors 132′ is coupled to the second interconnect structure 100′ ofthe packaged semiconductor device 150 in some embodiments.

In some embodiments, the second interconnect structure 100′ may comprisesimilar elements as described for the first interconnect structure 100(i.e., interconnect structure 100 shown in FIG. 11). For example, thesecond interconnect structure 100′ may include an RDL 106′ thatcomprises a plurality of conductive lines 108′ and conductive vias 108′.UBM pads 112′ that comprise a surface with an increased second surfaceroughness may be coupled to some of the conductive lines 108′ and/orconductive vias 108′. A connector 132′ may be coupled to each of the UBMpads 112′. In some embodiments, the plurality of connectors 132′ is notcoupled to the second interconnect structure 100′. In some embodiments,the second interconnect structure 100′ may not include UBM pads 112′having an increased second surface roughness.

A plurality of the connectors 132 and/or a plurality of the connectors132′ may be used to couple the packaged semiconductor device 150 toanother device, another packaged semiconductor device 150, or to a boardor other object in an end application, for example. The plurality ofconnectors 132 and/or the plurality of connectors 132′ may be used tocouple the first interconnect structure 100 or the second interconnectstructure 100′, respectively, of the packaged semiconductor device 150to a packaged integrated circuit, as another example.

In some embodiments, to form the second interconnect structure 100′, thepreviously described carrier 102 may comprise a first carrier 102, andafter the formation of the first interconnect structure 100, a secondcarrier (not shown) may be attached to the first interconnect structure100. The first carrier 102 is removed, and the second interconnectstructure 100′ is formed over the second side of the integrated circuitdie 152, the through-vias 156, and the molding material 154. The secondcarrier is then removed, and the plurality of packaged semiconductordevices 150 are then singulated. The first interconnect structure 100and the second interconnect structure 100′ may provide electricalconnections in a horizontal direction for a plurality of packagedsemiconductor devices 150 in some embodiments, for example. The secondinterconnect structure 100′ may comprise back-side routing, and thefirst interconnect structure 100 may comprise front-side routing, orvice versa, e.g., relative to the integrated circuit die 152, for thepackaged semiconductor devices 150 in some embodiments.

The methods of packaging semiconductor devices using one or morecarriers 102 described herein are merely examples: the integratedcircuit dies 152 may be packaged using different methods or orders ofmethods of a packaging process.

In some embodiments wherein a second interconnect structure 100′ isincluded, another packaged integrated circuit or semiconductor devicemay be coupled to the first interconnect structure 100 and/or the secondinterconnect structure 100′ of the packaged semiconductor device 150,for example.

For example, FIG. 14 is a cross-sectional view of a package-on-package(POP) device 170 in accordance with some embodiments. The POP device 170includes a packaged semiconductor device 150 that is inverted from theview shown in FIG. 12, for example. The POP device 170 includes apackaged semiconductor device 150 shown in FIG. 13 that has been coupledto another packaged semiconductor device 160 using a plurality ofconnectors 132′ coupled to the second interconnect structure 100′.

To manufacture the POP device 170, in some embodiments, before thepackaged semiconductor devices 150 shown in FIG. 13 are singulated, andafter the second interconnect structure 110′ is formed, a plurality ofthe second packaged semiconductor devices 160 is provided, and each ofthe plurality of second packaged semiconductor devices 160 is coupled toone of the first packaged semiconductor devices 150 using the pluralityof connectors 132′. The plurality of second packaged semiconductordevices 160 is coupled to the unsingulated plurality of first packagedsemiconductor devices 150 by a method such as manually by an operator ortechnician, by the use of an automated machine such as a pick-and-placemachine, or other methods. The eutectic material of the connectors 132′is heated, reflowing the eutectic material, and after the eutecticmaterial cools, the second packaged semiconductor devices 160 areelectrically and mechanically coupled to the first packagedsemiconductor devices 150. The plurality of first packaged semiconductordevices 150 is then singulated to form a plurality of the POP devices170, one of which is illustrated in FIG. 14.

The second packaged semiconductor device 160 may comprise a substrate162 that includes a plurality of contact pads disposed on. The pluralityof contact pads is disposed on a top surface and a bottom surface of thesubstrate 162 in FIG. 14, for example. The substrate 162 may include oneor more interconnect structures (not shown) formed thereon that providehorizontal connections for the second packaged semiconductor device 160in some embodiments. The substrate 162 may also include a plurality ofthrough-vias (also not shown) formed therein. One or more integratedcircuit dies 152 b may be coupled to a top surface of the substrate 162.The second packaged semiconductor device 160 comprises two verticallystacked integrated circuit dies 152 b in some of the embodiments shownin FIG. 14, for example. Two or more integrated circuit dies 152 b mayalso be packaged together horizontally in the second packagedsemiconductor device 160 in some embodiments, not shown.

In some of the embodiments shown in FIG. 14, the integrated circuit dies152 b are coupled to a plurality of contact pads disposed on the topsurface of the substrate 162 by bond wires 164. The bond wires 164 andthrough-vias in the substrate 162, if included, provide verticalelectrical connections for the second packaged semiconductor device 160in some embodiments. A molding material 166 is disposed over theintegrated circuit dies 152 b, the bond wires 164, and the substrate162. The molding material 166 may comprise similar materials andformation methods as described for the molding material 154 of the firstpackaged semiconductor device 150, for example.

In some embodiments, the integrated circuit die or dies 152 b of thesecond packaged semiconductor device 160 may comprise memory devices,such as dynamic random access memory (DRAM) devices, for example. Theintegrated circuit dies 152 b may also comprise other types of memorydevices and/or other types of devices. The integrated circuit dies 152 bmay be packaged in a wire bond type of package as shown in FIG. 14, orthe integrated circuit dies 152 b may be packaged in other types ofpackages and using other types of packaging techniques. The secondpackaged semiconductor device 160 may also comprise a similar type orthe same type of package as the first packaged semiconductor device 150.The second packaged semiconductor device 160 may comprise UBM pads 112having the increased second surface roughness 118, for example.

The POP device 170 may be coupled to another device or object using theplurality of connectors 132 disposed on the bottom surface of the POPdevices 170 that are coupled to the interconnect structure 100, e.g.,using a surface mount technology (SMT) process. In some embodiments, thePOP devices 170 may be coupled to a substrate or PCB 182, as shown inFIG. 14, forming a chip-on-wafer-on-substrate (CoWoS) device 180.

In some embodiments, the integrated circuit dies 152 a of the firstpackaged semiconductor device 150 may comprise logic devices orprocessors, and the interconnect structure 100 of the first packagedsemiconductor device 150 comprises fan-out wiring, e.g., in someembodiments wherein the second integrated circuit dies 152 b comprisememory devices such as DRAM devices, forming an InFO POP device 170. Thefirst integrated circuit dies 152 a, the second integrated circuit dies152 b, the first packaged semiconductor device 150, and the secondpackaged semiconductor device 160 may also comprise other types ofdevices, and the connector pad structures 101 comprising a plurality ofUBM pads 112 with the increased second surface roughness 118 describedherein may also be implemented in other types of applications.

FIG. 15 is a flow chart 190 of a method of forming a connector padstructure 101 (see FIG. 3) in accordance with some embodiments of thepresent disclosure. In step 192, a UBM pad 112 is formed, as also shownin FIG. 1. In step 194, the UBM pad 112 is exposed to a plasma treatment114, as shown in FIGS. 1 and 2. In step 196, a polymer material 120 isformed over a first portion 122 of the UBM pad 112, leaving a secondportion 124 of the UBM pad 112 exposed, as shown in FIG. 3.

Some embodiments of the present disclosure are advantageouslyimplementable in and are particularly beneficial when used in POPdevices, in some applications. The packaged semiconductor devices maycomprise POP devices 170, system-on-a chip (SOC) devices, CoWoS devices,or other types of three dimensional integrated circuits (3DICs) in someembodiments, as examples. Some embodiments of the present disclosure arealso beneficial for and may be implemented in other types of devicesthat include interconnect structures and fan-out structures, as otherexamples. Some embodiments are also beneficial in ball mountapplications and/or connector mounting applications, for example.

Some embodiments of the present disclosure include connector padstructures and interconnect structures that include the UBM pads havingan increased second surface roughness resulting from the plasmatreatment, and methods of formation thereof. Other embodiments includepackaged semiconductor devices that include the connector pad structuresand interconnect structures that include UBM pads having the increasedsecond surface roughness resulting from the plasma treatment, andmethods of packaging thereof.

Advantages of some embodiments of the present disclosure includeproviding low cost methods of improving reliability performance ofconnector pad structures and interconnect structures of packagingdevices. Plasma treatment of a UBM pad surface and a low-activity fluxare used to prevent or reduce IMC penetration to a polymer material andUBM pad surface interface. The plasma treatment roughens the UBM padsurface, which may improve adhesion, and which prevents or reducesdelamination between the polymer material and UBM pad interface regionin some embodiments. The more robust interface between the polymermaterial and the UBM pad results in reduced reliability test failureissues in some embodiments, for example.

Improved reliability interconnect structures with fan-out structures areachieved in some embodiments. Treatment costs for various materiallayers of connector pad structures and interconnect structures can belowered in some embodiments, for example. Ball mount processes (e.g., ofthe connectors) with high yields are advantageously achievable byimplementing some embodiments of the present disclosure. Furthermore,the methods and structures described herein are easily implementableinto existing interconnect structure and packaging process flows andstructures.

In some embodiments, a method of forming a connector pad structureincludes forming a UBM pad, and increasing a surface roughness of theUBM pad by exposing the UBM pad to a plasma treatment. A polymermaterial is formed over a first portion of the UBM pad, leaving a secondportion of the UBM pad exposed.

In some embodiments, a method of forming an interconnect structureincludes forming an RDL, and forming a UBM pad over a portion of theRDL. A top surface of the UBM pad has a first surface roughness. Themethod includes altering the first surface roughness of the top surfaceof the UBM pad to a second surface roughness, the second surfaceroughness being greater than the first surface roughness. A polymermaterial is formed over a first portion of the UBM pad. A connector isformed over a second portion of the UBM pad. A material of the connectoris reflowed.

In some embodiments, an interconnect structure includes an RDL and a UBMpad disposed over a portion of the RDL. A surface of the UBM pad has asurface roughness of about 0.18 μm to about 0.25 μm. A polymer materialis disposed over a first portion of the surface of the UBM pad, and anIMC is disposed over a second portion of the surface of the UBM pad. Aconnector is disposed over the IMC.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A structure comprising: a first redistributionlayer (RDL); an underball metallization (UBM) pad disposed over aportion of the first RDL, a rough surface of the UBM pad having asurface roughness, wherein the surface roughness is approximately 0.18μm to approximately 0.25 μm; a polymer material disposed over a firstportion of the rough surface of the UBM pad; an intermetallic compound(IMC) disposed over a second portion of the rough surface of the UBMpad; and a connector disposed over the IMC.
 2. The structure of claim 1,wherein the connector comprises Sn.
 3. The structure of claim 2, whereinthe IMC comprises CuSn.
 4. The structure of claim 1, further comprisingan integrated circuit die coupled to the RDL, wherein portions of theRDL are coupled to contact pads of the integrated circuit die.
 5. Thestructure of claim 4, further comprising: a molding material disposedaround the integrated circuit die, the RDL extending over the integratedcircuit die and the molding material; and a plurality of through viasdisposed within the molding material.
 6. The structure of claim 5,wherein the integrated circuit die comprises a first side and a secondside opposite the first side, wherein the first RDL is proximate thefirst side of the integrated circuit die, and further comprising asecond RDL proximate the second side of the integrated circuit die. 7.The structure of claim 6, further comprising a packaged integratedcircuit coupled to the first RDL or the second RDL.
 8. A semiconductordevice comprising: an integrated circuit die comprising a firstconnector pad and a second connector pad; a first underballmetallization (UBM) pad electrically coupled to the first connector pad,the first UBM pad comprising a first rough surface, the first roughsurface having a first surface roughness, wherein the first surfaceroughness is approximately 0.18 μm to approximately 0.25 μm; a secondUBM pad electrically coupled to the second connector pad, the second UBMpad comprising a second rough surface, the second rough surface having asecond surface roughness, wherein the second surface roughness isapproximately 0.18 μm to approximately 0.25 μm; a first polymer materialdisposed over a first portion of the first rough surface of the firstUBM pad; a second polymer material disposed over a first portion of thesecond rough surface of the second UBM pad, the first polymer materialbeing separate from the second polymer material; a first connectordisposed over the first UBM pad; a second connector disposed over thesecond UBM pad; a first intermetallic compound (IMC) interposed betweena second portion of the first rough surface of the first UBM pad and thefirst connector; and a second IMC interposed between a second region ofthe second rough surface of the second UBM pad and the second connector.9. The semiconductor device of claim 8, further comprising a moldingmaterial disposed around the integrated circuit die.
 10. Thesemiconductor device of claim 9, further comprising a plurality ofthrough vias disposed within the molding material.
 11. The semiconductordevice of claim 10, wherein the first UBM is laterally over the moldingmaterial.
 12. The semiconductor device of claim 9, further comprising aninsulating material layer disposed over the integrated circuit die andthe molding material, wherein a bottommost surface of the first polymermaterial and a bottommost surface of the second polymer material arelower than an uppermost surface of the insulating material layer. 13.The semiconductor device of claim 8, wherein a portion of the firstpolymer material is formed on sidewalls of the first UBM pad and aportion of the second polymer material is formed on sidewalls of thesecond UBM pad.
 14. The semiconductor device of claim 13, wherein theportion of the first polymer material is along a periphery of the secondportion of the first UBM pad and the portion of the second polymermaterial is along a periphery of the second portion of the second UBMpad.
 15. The semiconductor device of claim 8, wherein the first UBM padis electrically coupled to the first connector pad through a firstplurality of conductive lines and a first plurality of conductive vias.16. A semiconductor device comprising: an integrated circuit diecomprising a first side and a second side opposite the first side, thefirst side comprising a plurality of contact pads; a first interconnectstructure on the first side of the integrated circuit die, the firstinterconnect structure comprising: a plurality of first underballmetallization (UBM) pads, each of the plurality of first UBM padscomprising a first rough surface having a first surface roughness,wherein the first surface roughness is approximately 0.18 μm toapproximately 0.25 μm; and a plurality of first polymer structures, eachof the plurality of first polymer structures being disposed over a firstportion of the first rough surface of respective ones of the pluralityof first UBM pads; a second interconnect structure on the second side ofthe integrated circuit die, the second interconnect structure comprisinga plurality of second UBM pads, wherein at least one of the plurality ofsecond UBM pads is electrically coupled to a second subset of theplurality of first UBM pads by a through via; a plurality of firstconnectors, each of the plurality of first connectors disposed over asecond portion of the first rough surface of respective ones of theplurality of first UBM pads; and a plurality of second connectors, eachof the plurality of second connectors disposed over respective ones ofthe plurality of second UBM pads.
 17. The semiconductor device of claim16, further comprising a molding material disposed around the integratedcircuit die.
 18. The semiconductor device of claim 17, wherein thethrough via is disposed in the molding material.
 19. The semiconductordevice of claim 16, wherein each of the plurality of second UBM padscomprise a fourth rough surface having a second surface roughness,wherein the second surface roughness is approximately 0.18 μm toapproximately 0.25 μm, further comprising a plurality of second polymerstructures, each of the plurality of second polymer structures isdisposed over a first portion of the fourth rough surface of respectiveones of the plurality of second UBM pads, wherein the plurality ofsecond connectors is disposed over a second portion of the fourth roughsurface of respective ones of the plurality of second UBM pads.
 20. Thesemiconductor device of claim 16, wherein the first interconnectstructure further comprises a plurality of intermetallic compounds (IMC)interposed between the plurality of first UBM pads and the plurality offirst connectors.